Plastic foam sheet material has for years been used in various configurations as padding to absorb impact for providing safety in various types of sports activities. One use of plastic foam sheet material is for frame padding on trampolines. For example, it has been customary to provide safety padding with thick, flat sheets of plastic foam encased in vinyl bags secured around the outer perimeter of the trampoline. Many trampolines in use today are of circular shape in which the frame padding comprises arc shaped segments of flat plastic foam pieces encased in vinyl and held securely in place around the curved outer periphery of the trampoline. The padding for a circular trampoline can be improved by shaping the segments of plastic foam to form curved wall sections along their outer edges, so that each segment has a flat portion which faces upwardly and extends over the suspension spring region of the trampoline, with the curved outer wall section extending over and around the outer frame member of the trampoline.
Marketplace realities are such that the cost of manufacturing the frame padding for a trampoline should not exceed a certain proportion of the total equipment cost. Processing improvements in shaping the plastic foam padding can reduce manufacturing costs. A beneficial result of lower production cost can be the use of more cushioning material in the padding and resultant greater improvements in safety.
Plastic foam padding segments with curved outer wall sections can be made by shaping each piece of material in a clam shell mold. The material can be heated, shaped and cooled in the mold; or it can be heated, molded and then cooled outside the mold. In either instance, tooling costs are high, and substantial amounts of time are taken up between mold cycles, which adds to production costs.
The present invention provides a high speed process for continuous production of improved plastic foam padding material having curved outer wall sections suitable for use as frame padding for trampolines. The continuous process avoids the tooling costs and delay time that occurs between mold cycles in a conventional in-mold process for making foam parts with curved outer wall sections. By improving the speed of production, the cost savings resulting from lower production costs make it possible to use more padding material for the same cost, resulting in greater safety.
Although the invention has been described with reference to plastic foam padding for trampolines, principles of the invention are applicable to other uses of similar padding material as well as a process generally adapted for fabricating plastic foam sheet material with a compound radius.